Is Premium gas necessary?

[ammolab]

Originally Posted By: Jarlaxle
Originally Posted By: ammolab
Regular may do you just fine. My wife's 250 NINJA and my BMW K75C both spec and run fine on regular gas and making 100bhp/liter to boot.

Note that 86RON (Euro spec) is about 90.5 octane as measured on US pumps.



Formula for converting US to EURO octane
And reversing that forumula, wet get: RON = US*(22/21)

US (R+M)/2 EURO RON
87 91.1
88 92.2
89 93.2
90 94.3
91 95.3
92 96.4
93 97.4
94 98.5
95 99.5
96 100.6
97 101.6
98 102.7
99 103.7
100 104.8


No, that's backwards: the Japan/Euro RON numbers are HIGHER than the US (R+M/2) pump octane numbers. I recall 91RON is 87 here.


Chart is RIGHT and you are RIGHT: chart shows RON numbers HIGHER than USA pump listings.

 

[FastGame]

My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.

 

[HerrStig]

Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.
I don't see how VVT can control combustion chamber volume. SAAB tried a variable volume combustion chamber in an I4 but it required a hinge on one side of the head. Didn't work out well.

 

[FastGame]

Originally Posted By: HerrStig
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.
I don't see how VVT can control combustion chamber volume. SAAB tried a variable volume combustion chamber in an I4 but it required a hinge on one side of the head. Didn't work out well.


http://www.enginebuildermag.com/2014/01/the-inner-workings-of-variable-valve-timing/

Even my old KZ 1000 compression ratio is dependent on the cam profile.

 

[Cujet]

My high compression, high RPM Suzuki SV1000s only requires regular. 11.3 to 1 compression, nearly 4 inch diameter piston. Every once in a while, I'll hear a "ping" on regular but it's rare. I sometimes use 90 octane "rec" gas as it runs better without ethanol. Both regular and premium contain ethanol around here. The SV cannot adjust for ethanol content, as it does not have an oxygen sensor. It has a slight delay in throttle response with fuel of any octane, if that fuel contains ethanol.

Otherwise, I really can't tell much difference.

 

[alarmguy]

Originally Posted By: ammolab
Premium gas resists "pre"ignition. I have never seen proof that it resists the spark provided by the ignition system to the point that it does not "fully ignite".

It surely is a waste of money but I don't see "deposits" remaining in all those engines built for regular that are pumped full of premium. It's pretty hard to make gas partially burn in a proper running internal combustion engine.


It might be hard to do but it can happen, using premium gas in an engine calling for regular. I know the vstar 1300 can have an issue with this.
Some automobiles can too and their ECMs are much more sophisticated then a motorcycle.

I am not saying dont use premium but there are reasons to follow the owners manual if your engine is running properly as it can be detrimental to not follow the manual.

Click here for the source

Here is the quote. (just trying to help the OP)
" Fuel octane and the quality or type of fuel used in an engine can also be an area of concern. Driveability Index (DI) is a measure of gasoline’s total volatility, or tendency to vaporize completely. A high DI number is less volatile than a low number. Premium grade gasoline is rated at a higher DI (less volatile) than regular or midgrade gasoline. Since fuels with a higher DI number or octane burn more slowly, higher compression ratio engines typically use higher octane fuels to avoid heat-induced preignition. Conversely, when using a high-octane (less volatile) fuel than an engine was designed for, fuel will burn too slowly, resulting in incomplete combustion, increased carbon deposits and driveability concerns such as increased cold start, warm-up sags, hesitations and stalling at moderate ambient temperatures."

 

[steveh]

I use premium because its the only gas I can get that is E0.

 

[Ducman]

Originally Posted By: alarmguy
Using premium gas in an engine designed for regular can only hurt performance not give you better performance.
Not only that, using premium gas in an engine designed for regular can and most likely will GREATLY increase the chances of harmful deposits in your cylinders.

The reality is regular gas is more explosive/easier to ignite then premium gas. (most people think the other way around because the word premium)

In a high compression engine, premium gas is required because premium gas is harder to ignite. This prevents pre ignition in the cylinder which prevents the fuel mixture from exploding (igniting) before the spark plug fires.

SO the ONLY thing about "Premium" gas is the premium price, it is NOT a better fuel then regular gas, its only a fuel that is harder to ignite, due to lower production numbers and higher profits, premium gas is only premium in price, no better then regular, just different application.

Using premium gas in an engine that requires regular gas, simply may mean the gas does not get a chance to fully ignite and may/many times, leaves behind deposits in the cylinder and piston.


I would be inclined to disagree with this premise.

Of course I can only speak from my experience here in OZ, but the highest octane premium fuels(98 ron) here are different from the normal premium fuel(95 ron) in that they have a higher dosage of additives to help keep the fuel system, valves, spark plugs and combustion chambers cleaner for optimum engine performance.
Testing has demonstrated the advantages of the higher concentrations of the additives.

There is no doubt that an engine which is designed and tuned to run on a lower octane fuel, will not derive any power advantage in going with the higher octane fuel, and may actually produce less power with the higher octane fuel under most normal driving circumstances.
The other side of the equation is that higher efficiency in day to day driving conditions will result from cleaner valves, spark plugs and combustion chambers.

Of course, the question remains to be answered whether it's worth the premium in price per litre.
I suspect it's better value to use the correct minimum fuel grade for the vehicle, and add a good quality fuel additive as required to keep things clean.

 

[Mik]

Originally Posted By: HerrStig
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.
I don't see how VVT can control combustion chamber volume. SAAB tried a variable volume combustion chamber in an I4 but it required a hinge on one side of the head. Didn't work out well.


VVT does not control combustion chamber volume, but it does exercise an effect on actual cylinder pressure (low overlap builds more pressure while lots of overlap bleeds off pressure), so when the cylinder pressure is up (low cam overlap), the added octane is an insurance policy against detonation

 

[HerrStig]

Originally Posted By: FastGame
Originally Posted By: HerrStig
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.
I don't see how VVT can control combustion chamber volume. SAAB tried a variable volume combustion chamber in an I4 but it required a hinge on one side of the head. Didn't work out well.


http://www.enginebuildermag.com/2014/01/the-inner-workings-of-variable-valve-timing/

Even my old KZ 1000 compression ratio is dependent on the cam profile.
How does cam profile relate to the diameter of the piston and the length of the connecting rod in any way which could change compression ratio, which is calculated based on those measurements, and not on things "bleeding off"?
The same could be said of throttle opening or whether or not the air filter were clogged.

 

[WANG]

Originally Posted By: HerrStig
Originally Posted By: FastGame
Originally Posted By: HerrStig
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.
I don't see how VVT can control combustion chamber volume. SAAB tried a variable volume combustion chamber in an I4 but it required a hinge on one side of the head. Didn't work out well.


http://www.enginebuildermag.com/2014/01/the-inner-workings-of-variable-valve-timing/

Even my old KZ 1000 compression ratio is dependent on the cam profile.
How does cam profile relate to the diameter of the piston and the length of the connecting rod in any way which could change compression ratio, which is calculated based on those measurements, and not on things "bleeding off"?
The same could be said of throttle opening or whether or not the air filter were clogged.


I believe that they are referring to "dynamic compression ratio" and you are referring to "static compression ratio". They aren't wrong, and neither are you*.

*except for conrod length being a factor in calculating static CR, that's not a thing

 

[ammolab]

Premium gas will load up low compression engines with deposits from poor burn?

What about Turbo engines? I owned an 1984 Turbo Colt and a 2000 Audi S4 BiTurbo. Both running less than 9 to 1 compression and both requiring premium gas for running on boost. However when running for hours at steady throttle (negative manifold vacuum/low cylinder filling) these low compression engines on premium gas do great.

Plenty of turbo engines from the 1970s to now have run like this without "deposits" as have plenty of Texas pickups built for regular but pumped full of premium by owners who can "afford the best"

 

[David_g]

Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.

The link you provided refers to "effective compression ratio" which I expect is what WANG called "dynamic compression ratio". Without qualifiers, "compression ratio" is what WANG called "static compression ratio", and it is not dependent on valve timing.

Dynamic compression ratio won't be higher than the actual (static) compression ratio of the engine. So if you wonder how high it can go, well it can't go any higher than that. If you look up numbers for that engine maybe you'd get the static compression ratio.

 

[FastGame]

Originally Posted By: David_g
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.

The link you provided refers to "effective compression ratio" which I expect is what WANG called "dynamic compression ratio". Without qualifiers, "compression ratio" is what WANG called "static compression ratio", and it is not dependent on valve timing.

Dynamic compression ratio won't be higher than the actual (static) compression ratio of the engine. So if you wonder how high it can go, well it can't go any higher than that. If you look up numbers for that engine maybe you'd get the static compression ratio.


Call Kawasaki up and ask why the Concours 14 needs 91 octane when the static compression ratio is 10.7:1 vs the ZX14 12.1:1. They will answer because the C-14 has VVT and the ZX doesn't and both require 91 minimum, they will throw in the C-14 VVT's dynamic dynamic compression ratio thing....

Don't shoot the messenger, I'm only doing what the book says and what other C-14 owners found out though their questioning the 91 minimum.

 

[SR5]

As Ducman says, the fuels in Oz are 91, 95 and 98 RON.

They sell the higher premium fuels (98 and 95 RON) for all vehicles, as (they claim) these fuels have special additives to clean the fuel system / injectors / carbs. / intake valves etc. and control deposits. So here anyway, they all claim that engines run cleaner on the premium fuel, because it's a total package, not just octane rating.

I have run my CBR 600 on all three.
With 91 RON, I sometimes got pre-ignition. But no pinging problems with 95/98 RON.

However I did notice that sometimes (rarely) my bike ran rough on 98. I couldn't work it out. Then I was told that the higher octane fuel absorbed more water, and these rough times were during the wet season. So I switched to 95 and the rough running went away. By rough I mean it would miss on a cylinder when cold, but was OK when it warmed up.

In the end I found 95 RON was my sweet spot. So I say experiment a little with the fuels you have in your area.

 

[David_g]

Originally Posted By: FastGame
Don't shoot the messenger, I'm only doing what the book says and what other C-14 owners found out though their questioning the 91 minimum.

Didn't mean it to sound like that. Was trying to point to an answer to how high it goes question. I'd do what the manual said too.

You answered a question of mine as well. Lat night I was talking to a friend about valve check/adjust he's about to do on his ZX14. Previously a mechanic who has come to my home to do several valve adjustments for me, said he'd do valve adjustment on my friends ZX10R, but not the ZX14. I'll assume that like your C14, the ZX14 has VVT and that makes valve adjustment more time-consuming. More work than my guy wanted to deal with in a mobile mechanic job.

 

[alarmguy]

Originally Posted By: SR5


They sell the higher premium fuels (98 and 95 RON) for all vehicles, as (they claim) these fuels have special additives to clean the fuel system / injectors / carbs. / intake valves etc. and control deposits. So here anyway, they all claim that engines run cleaner on the premium fuel, because it's a total package, not just octane rating.




Thats from the old days, real old days, like when Coke used to claim their soda "cures what ails you"
Any quality gas uses the same additives no matter if regular or premium. In fact some/many have started advertising that. If using premium only for that reason and someone wants to feel better simply chose a fuel company that states the same additives in all grade fuels. Been that way for decades now and the majors have now started to come out and say it. Lets face it a very small percentage of the population needs premium and all cars do fine on all quality gasoline, no matter the brand.
All premium gas is simply gas that is harder to ignite. No more or less.

 

[BusyLittleShop]

Our knowledge about gasoline hasn't made much progress; because some
people are still buying more octane than they need...

A motorcycle manufacture's octane rating has to take into account the
vast elevation changes in the USA... that means they must pick an
octane based on the fact that you may venture from the highs of
Colorado to lows of the Pacific Coast... your engine is more likely to
ping next to Pacific Coast than in the rarefied air of Colorado...
that means no matter what octane you choose... listen for pings... if
you hear pings go up one octane... no pings go down one octane... all
in all you may end up burning 87 octane even though the manufacture
recommends 91 octane... you just live at the correct altitude that
produces no pings...

Most engines sport 11.5 to 1 compression and will still burn 87 happily...
you may hear your combustion chamber ping once or twice each year...
that's not enough to go up one octane... especially if the ping happens on
the side of a steep hill in San Francisco while you're incinerating the clutch
to get moving from a stop light...

 

[THE_TROTS]

Those of us that have old bikes with mechanical slide carbs and centrifugal spark advancers may benefit from higher octane gasoline, especially if you like to accelerate without downshifting.

CV carbs, and later fuel injection and electronic spark advance eliminated a lot of the need for premium gas in motorcycles.

 

[JetStar]

Originally Posted By: pbm
While looking through the owners manual of my newly acquired 1998 Virago I noticed that 'Regular' (86RON) gasoline is spec'd. I always thought that Premium was called for in motorcycles but now I'm wondering if it's necessary.
I know that running Premium in a car that calls for Regular is a waste and I'm wondering if the same is true here?

Opinions wanted....thanks.


Use what your manual tells you. My FZ1 has 11.5:1 compression and never pings on regular. I think it depends on combustion chamber design and perhaps cooling more than anything else. If your bike is in a proper state of tune, you'll be fine.